1. Field of the Invention
The present invention relates to a vinylidene fluoride-based polymer dielectric having a combination of a high dielectric constant and a low dielectric dissipation factor.
2. Description of the Prior Art
Polymer dielectrics are widely used, for example, as materials for electric capacitors or condensers mainly of small sizes, because they can be easily formed into films. Polymer dielectric materials well known heretofore include polyethylene, polyethylene terephthalate (hereinafter abbreviated as "PET"), polycarbonate, and polystyrene. Among these, PET has both a relatively low dissipation factor (hereinafter referred to as "tan .delta.") of about 0.6% at 20.degree. C. and 1 kilo-hertz (KHz), and an excellent film forming property, and is widely used as a useful polymer dielectric material.
However, while PET has a low tan .delta., it also has a small dielectric constant of about 3.2 at 20.degree. C. and 1 KHz. Moreover, PET is relatively hygroscopic and therefore has a drawback that its dielectric properties vary according to change in enviromental conditions. On the other hand, polyvinylidene fluoride (hereinafter abbreviated as "PVDF") has the highest level of dielectric constant among the synthetic polymers, has an excellent shapability or processability and also has a low hygroscopicity which is an advantageous feature as a dielectric material when compared with PET. However, PVDF has a tan .delta. of about 1.0% or above which is larger than about 0.6% for PVDF, and is not desirable as a material for usage requiring small dielectric loss.